1. Field of the Invention
The present invention relates to an endoscope light source apparatus which can feed illuminating light to a scope provided with a frame sequential type imaging means, a scope provided with a synchronous type imaging means and a fiberscope (optical scope).
2. Related Art Statement
Recently, there is extensively used an endoscope (called also a scope in the following) whereby, by inserting an elongate insertable part through a body cavity, organs within the body cavity can be observed and as required, by using a treating tool inserted through a treating tool channel, various curing treatments can be made. As an endoscope, there are suggested optical type endoscopes (called also fiberscopes in the following) wherein an image is transmitted by a bundle of optical fibers and observed with the naked eye and electronic type endoscopes (called also electronic scopes in the following) wherein an image is taken by such a solid state imaging device of such a charge coupled device (CCD). Furthermore, an endoscope can be classified into a frame sequential type electronic scope which sequentially switches incident light for an imaging device to color light of such as R(red), G(green) and B(blue) in each picture, and a synchronous type electronic scope which makes each picture element of the imaging device a disposition of such as R, G and B by providing mosaic filters of such as R, G and B on the front surface of the imaging device.
That is to say, in the frame sequential type electronic endoscope, illuminating light from a light source is fed to a light guide sequentially through color transmitting filters which transmit the colors such as R, G and B so that an object is illuminated by the illuminating light of R, G and B sequentially transmitted by the light guide and imaged. On the other hand, in the synchronous type electronic scope, an object is illuminated by white light transmitted through the light guide and imaged by the solid state imaging device provided with mosaic filters. In this manner, the illuminating method of the frame sequential type electronic scope is different from the illuminating method of the synchronous type electronic scope and the light source which feeds illuminating light adapted itself to each scope is needed.
Then, in the official gazette of Japanese Patent Laid Open No. 2927/1987, it is proposed that one apparatus feeds illuminating light adapted to each scope by means of making a rotary filter having R, G and B color transmitting filters possible to be retreated from an optical axis. That is, in case the frame sequential type electronic scope is used, the rotary filter is interposed on the optical axis, and in case the synchronous type electronic scope and fiberscope are used, the rotary filter is retreated from the optical axis.
However, the illuminating light from the light source is reduced through transmitting the color transmitting filter of the rotary filter. The quantity of illuminating light fed to the light guide when the frame sequential type electronic scope is used, is different from the quantity of the illuminating light when the synchronous type electronic scope is used. Therefore, when the frame sequential type electronic scope is used, the quantity of light might be insufficient, and also, there was a problem that an incident end of the light guide is burnt when the synchronous type electronic scope and fiberscope are used.
Further, since it is impossible to obstruct the infrared rays of illuminating light sufficiently in the color transmitting filters, there was a problem that the color reproducibility in the frame sequential type electronic scope is not sufficient because of a spectral sensitivity characteristics of the solid state imaging device.